Multigap lightning arrester



Oct. 9, 1928.v

J. RL MCFARLIN MULTIGAP LIGHTNING ARRESTER Filed Jan. ll, 1922 JTTORNEYSPatented Oct. 9, 192.8.

UNITED STATES' PATENT orsi-ca JOHN ROBERT MCFARLIN; orPHILADELPHIA,PnNNsYLvANIAassiettes 'ro 'rRIcsnIwIon SUPPLIES COMPANY,por PHILADELPHIA, PENNsYLvenIn, A oon- 'PORATION OF FENNSYLVANIA. l

"Y MULTIGAP LIGHTNING ARRESTER,

Application niea-Januaryii, 1922: semi 110.528.491.

f My invention relates to lightning arresters of the so called multi-gaptype and my` primary obj ect is to provide improved means of highefficiency, as well as simple, convenient and durable construction, forprotecting electrical apparatus from 'lightning andother high voltagedisturbances, by discharging such disturbances to ground and effectivelypreventing a following' flowk of dynamic or line current from continuingthrough the arrester to ground.

Desiderata attained by my invention are high eciency in protectingelectri-cal aparatus from variousclasses of lightning or high voltagedisturbances; the capacity for successfully discharging charges Ioflight or heavy volume, relatively *lowv or high volt'- age and low orhigh frequency, and flexi- 1 bility in the assembly and adjustment ofits constituent parts with. adaptability toy etlicient operation undervarying conditions encountered in service. v v

My invention, prises an insulating on top containing a housing having asealed plate electrode provided with a lug, into which top thelead fromthe.

line wire passes to a connection with the lug, `and a bottom providedwith an yopeningk through which the lead from. the ground wire enters toa connectionrwith a plate electrode on said bottom, in ,combination witha series of dished conducting discs, a series of insulating andnon-inductive .resistance spools disposed between discs spaced therebyto vform spark gaps, varying in size and resistivity, and an .insulatingbolt passing ythrough said plate electrodes', conducting discs andresistance spools to clamp them together.

The characteristic features of my invention are fully set forth in thefollowing description vand` the accompanying drawings in illustrationthereof. Y i In the drawings, Fig. 1 is an elevation of a lightningarresterembodying ments; FigQ is a centrallongitudina'l sectional viewof same, land- Fig. 3 isajbroken section mainly on the lineBX-BX'offFig. 2.

In the form of my improvements :illustrated in the drawings, aninsulating housing 1, adapted to be supported as on apole, has a cap 2cemented on its top;v A plate electrode 3, containing a central opening4, is fixed bythe cap 2 on thepbody 1 and has in its preferred form,comthe resistance spools my improve;

a part 5 projecting- `beyond the lbody into the recess 6 of thecap forconnection through the recess with the lead 7 to the line wire.v f

A dished metal disc or ring 8, containing the 'central aperture 9 andhaving the flat peripheral ridge 1,0, has its plane central or bodyportion'A disposed in engagement with the lower surface ofzthe plate 5,with the circular` peripheral Vridge extending downwardly.V Aninsulating spool 11y isplaced in engagement with the' body portion ofthis disc, within its downwardly projecting. v

ridge.

placed in engagementl with the insulating spool 11 in reverse relationto the first disc, with its circular ridge projecting'upwardly,

Af second similar metal disc 8 is the circular ridges of the twodiscsbeing so Y disposedas to form terminals with an air gap 12Vtherebetween. `Further similary discs 8 and spools 13 formed ofconductive material having a* relatively high ohmic resistance, as forrexample 100,000 ohnis each, are arranged in columnar relation concentricwith and similarly tothe arrangement ofthe prei viously described discs8 withthe spool 11;

the lbodies of the discsy between contiguous s poo'ls' beinginhcontact,v their. jecting inl opposite directions, and the air Agaps14 corresponding to the'spools 13 being less'than the gap y12, as hereshown.k

Metalfdiscs 15 like the discs v8, but with deeper ridges, are separatedby conducting spools 16k having a. relatively .low ohmic resistance asfork example 50 ohms each, thesev discs andspools being arranged asypreviously described so that'the plane surfacesof thediscs betweencontiguous spools are in contact and the discs separated by therespective spools have their ,ridges disposed inY opposite directions soas to provide air gaps 17 between them. f i

A plate electrode 18, supported Within the bottom `of the body 1, isengaged by the plane body portion ofthe lowermost disc 1.5, and theseveraldiscs and spools are clamped together by an insulating bolt V19ypassing centrally therethrough, nuts Aor4 clamping members 20 vand 21 onthe endsfof the bolt being disposed l inv recesses top and bottom of thehousing respectively. A lead 24 ltothe ground extends through an opening25 in the bottom of the housingk to a `connection with the electrode 18.f

'ridges pro-q QQand' 23 of thev This assembly secures accuracy of'relationship between the parts as Well as good electrical connections,While permitting ready assemblage in the desired relationship, readyadjustment of the relationship between the parts, and readysubstitutions to vary the character of the resistance and the number orcharacter of the air gaps, as may bel desirable by reason of the servicefor which the mechanism is to be used. Y

In operation, when the line to which the i arrester is connected isovercharged, the disohargeto ground takes Aplace through the arrester ina manner dependingon the frequency of the discharge, its volume andother characteristics.

l/'Vhen a slight accumulation of static ldischarges to ground, it Willytake the path through the parts 7 and 3 to the disc 3 in contact withthe latter, thence across the air gap 12, thence ythrough the engagingdiscs y between the contiguous spools 11 and 13, and

thence through the spools 13 and 16 by Way of the `discs vbetvveeii themto the loWermost disc 15, the plate 18. and the lead 24: to ground. Thisdischarge of static, in breaking down the air gap 12, ionizes the air betvv'een the corresponding discs 8 and thus permits a flow of dynamic ornormal current to ground through the path taken by the static discharge.But this 110W of dynamic current Will be very 'small being limited bythe combined resistance of all the spools in series, and Will beinterrupted bythe action of the air gap 12 at the first half cycle ofthe generator Wave, or Where-the flow Vreverses and passes through zerovalue.

.A heavier charge of static or lightning, in discharging through thearrester .to

ground, takes the path through the electri-` being expressed as'theproduct of theohmic resistance of the spool and the current in amperesflowing through the spool. ylVhen this voltage becomes high enough, itWill break down vthe air gap and as a consequence a large part of thedischarge Will take the path of least resistance across the gap ratherthan `through the spool. VThis discharge of static or lightning, inbreaking down the air ygap 12 and one or more ofthe air gaps 14, ionizesthe air in ythe respective gaps and so permits a flow of dynamic ornormal cur-` rent from line to ground over the same path taken `by thestatic discharge. This iiow of dynamic current Will be limited by thecombined resistance of all the spools 13 and 16 through Which it flowsand it will bevextinguished by the actions of the air gaps in its pathat the first half cycle of ythe gen- .'erator Wave, or Where the fiowllreversesand passes through zero value.

A still heavier charge of static or lightning, discharging through thearrester to ground, will take the path across all air gapsl 12 and 11.around the corresponding insulating spool 11 andfhigh resistance spools13, and thence, `depending on its volume, may take the path across .oneor more of the air gaps 17, thence through the consecutivespool orspools 16, the plate 18 and the lead 21 .to ground. Whether anydischarge will take the path across an airV gap corresponding to a spool16, or through such spoohwi-ll depend on the voltagebuilt up. across theends of the spool,this voltage whenv high enough breaking down the airgap and the discharge :therefore largely .taking the pathV of leastresistance across the gap vrather than through the spool itself. VThisdischarge of.

static or lightning, in breakingdownthe air gaps across Which it flows,ionizes vthe air in the respective gaps and so permits a Vflow ofdynamic or normal current from lineY to ground over .the :same staticdischarge.v rent will. be limited by the combined resistance of all theloW resistance :spools through Which it flows and Will be :extinguishedby the actions of the air gaps in its path at the first `half cycle ofthe `generator Wave, or Where theflovv .reverses and zero value.

It Will be evident that a large-part of an extremely heavy dischargelmay flovv through path taken iby the passes through' This flow ofdynamic cur-` the arrester over a direct air Agap path, suchl pathoffering .the Vgreatest freedom of dirscharge and consequently affordingthe vmost efiicient :protection -t0 electrical apparatus. In such case,the flou7 of dynamic ornorma'l current following the discharge to groundwill not *be limited by anyof the resistanceV spools -Within thearrester, Ibut the vfunctioning of the arrester is suoli ythat las theresist# ance spools are progressively 'eliminated from the dischargepath, additional air lgaps are automatically interposed in the path toleX- tinguish the fioW of' current. The flovv` being assumed to beextremely large, all ofthe air gaps act toelxtinguish the currentat thefirst half cycle of the generator Wave, or Where the floW reverses and`passes through Zero value. i

Thev flattened ridges -orterminals of the metal discs providev asubstantial areaf'roni Which discharges may occur, avoidingV the burningand pitting that takes place in angular and rounded terminals and thusprolonging the vlives of such discs.

The facesof the conducting spools 13 and 16 are covered with a coatingmaterial such as copper to afford good electrical contact between such.spools and the metal discs or spark gap electrodes engaged thereby;

In these spark gapelements, the construction is such that thespark takesplace between quite exposed surfaces as distinguishedv matically, toafford the utmost freedom in discharging static or lightning chargesfrom line to ground and the maximum protection to apparatus from chargesof widely vary! ing character. v

The mechanism shown and described, by

way of eXeinpliying an embodiment of my invention, may be variouslymodified, as by increasing or diminishing the number and spaces of theair or spark gaps; the number, resistivity and arrangement of the spoolsand otherwise within the scope of the claim.

Having described my invention, I claim:-

A lightning arrester comprising a plurality ot pairs of contacting gapelectrodes having oppositely projecting peripheral ridges,l

hollow spoolsvwithin said ridges and each spacing an electrode of onepair from an electrode of an adjacent pair, said spools being ofdifferent resistivities, and an insulating rod passing through saidspoolsl and spaced from the inner lsurfaces thereof, said rod havingthereon means for clamping said spools and electrodes together. n

In testimony whereof I have hereunto set my hand, this 9th day ofJanuary, 1922.

JOHNv ROBERT MCFARLIN.

